It is well known to use a coolant temperature indicator or temperature gauge with an internal combustion engine so that the operator can conveniently assess the engine operating temperature and estimate the likelihood that the engine may leave the range of acceptable conditions. However, with newer methods of controlling the coolant temperature, such as electronic thermostats and actively controlled fan speed, the coolant is maintained at such a precise temperature that the temperature gauge no longer provides information about the adequacy of the cooling system under current engine operating conditions. The operator cannot determine from the coolant temperature whether the cooling system is running at 10% or 98% of capability. Although displaying other parameters such as fan speed or thermostat position might allow an engine operator to make a more knowledgeable assessment, it would also increase the skill requirement of the operator. This is especially true for engines that are routinely operated over a range of speeds.